Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$56.86	7.574%	$61.1666	$61.17	$61.15	$61.20
Purchase #2	$61.74	4.367%	$64.4362	$64.44	$64.45	$64.40
Purchase #3	$182.58	5.823%	$193.2116	$193.21	$193.20	$193.20
Purchase #4	$147.56	13.572%	$167.5868	$167.59	$167.60	$167.60
Purchase #5	$34.91	13.317%	$39.559	$39.56	$39.55	$39.60
Purchase #6	$71.28	3.648%	$73.8803	$73.88	$73.90	$73.90
Purchase #7	$99.71	12.218%	$111.8926	$111.89	$111.90	$111.90
7 purchase totals =	$654.64		$711.7331	$711.74	$711.75	$711.80